1. Field of the Invention
This invention relates to a collimator for a radiation detecting device such as a scintillation camera used for medical diagnoses.
2. Description of the Prior Art
Radiation collimators are used in radiation detecting devices for channeling radiation between a source of radiation and a radiation sensitive transducer. An example of a radiation detecting device to which the present invention finds application is the Anger-type scintillation camera, the basic principles of which are explained in U.S. Pat. No. 3,011,057. The Anger camera is a nuclear radiation detecting device which is widely used in the medical field for analyzing the distribution of a gamma radiation emitting substance in a human body organ. The purpose of using a collimator with a radiation detecting device is to define radiation transmitting channels between a source of radiation (e.g. a human body organ) and a transducer (e.g. a scintillation crystal of an Anger camera) so that radiation emitted from spatial areas of the radiation source can be mapped to corresponding spatial areas of the transducer. The most commonly used collimator is the multi-channel collimator which comprises a number of radiation transmitting apertures or channels separated from each other by radiation opaque walls or septa.
Most collimators for gamma ray cameras are of a unitary construction. When they are mounted on the camera head, the viewing angle of the head with respect to the source of radiation is fixed. For many clinical studies, however, it is desirable to vary the aspect angle of the image of view. This can be done by moving the camera. This may, however, lead to degradation of the resolution of the image. For example, where the camera head is rotated when a parallel hole collimator is used, some parts of the collimator face may be at a greater distance from the patient (or organ of interest) than others which distorts the picture. To overcome such a problem, a variety of slanted channel collimators have been developed. Nevertheless, when a change in the viewing angle is desired, it cannot be done without repositioning the camera head or changing the collimator.